From: "Ara.T.Howard" <Ara.T.Howard@...>
Date: 2004-06-11T00:13:42+09:00
Subject: a __real__ drb question


now that i've already stuck my foot in my mouth, i'd like to ask a real drb
question.

say you've got a thread accessing an obj which is being served by drb:

   require 'drb/drb'

   mode = ARGV.shift || 'server'

   class Q
     def initialize; @q=[]; end
     def push obj; @q << obj; end
     def pop; @q.shift; end
   end

   case mode
     when 'server'
       q = Q.new
#
# is this safe?
#
       Thread.new{loop{ sleep 2; q.push Time.now }}

       DRb.start_service nil, q
       uri = DRb.uri
       puts "ruby #{ $0 } client #{ DRb.uri }"
       DRb.thread.join

     when 'client'
       uri = ARGV.shift
       DRb.start_service nil, nil
       q = DRbObject.new nil, uri
       loop do
         obj = q.pop
         p obj
         q.push 42
         sleep 0.5
       end
   end


my understanding is that access to the object via DRb is provided by multiple
synchronized threads.  eg. only one DRb thread would be accessing your object
at once so you generally don't need to consider thread coordination.  in this
case, however, i have a thread outside of DRb accessing the object - what sort
of coordination would this require?  perhaps it would be better to have the
thread obtain a DRbObject itself and allow the DRb library to handle all the
coordination?

eg.

....
     when 'server'
       q = Q.new
       DRb.start_service nil, q
       uri = DRb.uri
#
# safe?
#
       q = DRbObject.new nil, uri
       Thread.new{loop{ sleep 2; q.push Time.now }}

       puts "ruby #{ $0 } client #{ DRb.uri }"
       DRb.thread.join
....

comments?

-a
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